your not going to. typically portfolio margin is roughly 6:1 and some firms allow only 100k. some firms require more.
yes you can most prop firms will give you 6 to 1 you can get with 25k portfolio margin i wont give you any name google them call them and as if they can do that you will be surprised good luck
If you go to a prop firm then its not a 'portfolio margin' account. PM account will get u 6:1 leverage intraday and overnight with no s7 required. I believe the 100k minimum is imposed by the regulation so there is really no way around it.